1. Field of the Invention
This invention relates to automatic garage door operators, and more particularly to means for engaging and disengaging the drive mechanism of door operators.
2. Description of the Prior Art
Garage door operators are well known and are commonly used to automatically open and close upwardly acting overhead garage doors. These garage door operators, which are electric motor driven and usually remotely operated by radio control, provide considerable convenience to the motorist for powered, remote opening and closing of the garage door. The operators are usually actuated using a remote transmitting unit, which is typically carried in a vehicle, and is used to signal the controller of the garage door opener system to raise or lower the door, as the driver wishes.
Many different forms have been devised in the prior art to connect the door operator drive mechanisms to the garage door to be moved. Many garage doors are sectional garage doors of the overhead acting type which slide upwardly on a track to a position adjacent the ceiling of the garage. For these doors, the garage door operator includes a frame extending along the garage ceiling which provides a rail for a load carriage that moves longitudinally along the frame. A drive mechanism moves the load carriage, and in my instances, this drive mechanism includes a flexible drive member, and more particularly, a roller chain. The load carriage is pivotally connected to the top section of the sectional garage door. This same construction is also used with slab or one-piece garage doors which are pivoted to swing upwardly adjacent the garage ceiling when in an open position.
Garage door opener systems sometimes become inoperative either due to electrical power outage or, much more infrequently, due to mechanical malfunction. When the garage door opener system becomes electrically inoperative, the drive mechanism remains mechanically connected to the garage door, preventing it from being opened. On these rare occasions the electrically powered garage door operator cannot be used to open the door, so it must be disconnected from the door in order to open the door manually. The door operator thus must provide some means to disengage the door operator from the door so that the door may be manually operated.
A number of releasable connection mechanisms have been proposed for incorporation into the load carriages for selectively disconnecting or mechanically uncoupling the garage door from the drive mechanism. Some prior art release schemes disengaged the door arm pivotal connection and the load carriage. This disengagement permitted the L-shaped door arm to hang downwardly when disconnected from the load carriage and allowed the garage door to be opened and closed. However, these schemes had the very great disadvantage that the door arm, which is an L-shaped member that may be about two feet long and of heavy iron construction, was left pivotally attached to the upper end of the garage door. Thus, when the garage door was manually moved upwardly to an open position, if the user was not extremely cautious, the garage door arm could swing free and puncture a hole in the top of an automobile or in the rear window or windshield of the automobile parked in the garage. Still worse, the door arm could cause physically injury by hitting a person in the head or causing some other sever damage. This was all the more dangerous because electrical power failures only rarely occurred, and the person doing the garage door opening would forget from one time to the next that this potential hazard existed.
In other prior art devices the means to disconnect the garage door from the door operator was very unhandy or very awkward or very difficult to accomplish, was sometimes provided as an afterthought, and in many cases merely consisted of the removal of one of the pivot pins somewhere in the drive train.
A solution to these problems is shown in U.S. Pat. No. 3,630,094 to Carli which shows a selectable disengaging and engaging mechanism for a garage door operator which includes a lock bar that is yieldably urged toward engagement with a chain and which may be longitudinally moved and rotated so that a latch will latch the lock bar in a disengaged condition relative to the chain.
Other release mechanisms are shown in U.S. Pat. No. 3,051,014, issued to Houk, U.S. Pat. No. 3,722,141, issued to Miller, and U.S. Pat. No. 4,905,542, issued to Burm et al.
One problem with most prior art disengaging mechanisms is that they usually required moving an actuating member or handle in a horizontal direction in order to engage or disengage the carriage from the drive chain. Since the garage door operator is mounted to the garage ceiling, it is fairly high, and this horizontal action could be easily accomplished by most people of normal stature. It would be preferable to accomplish the engaging and disengaging action using only a vertical force, but this has heretofore not be possible.
Another problem with most prior art disengaging mechanisms is that the force required by the user to engage and disengage the carriage from the drive chain may be substantial due to the high load forces on the drive chain. The load forces in the direction of travel of the drive chain exceed the force needed to open and close the garage door, and these load forces can create substantial resistance to the engagement and disengagement of the carriage from the drive chain.